Neuropharmacology 37 (1998) 847–857 Nicotine prevents glutamate-induced proteolysis of the microtubule-associated protein MAP-2 and glutamate neurotoxicity in primary cultures of cerebellar neurons Marı ´a-Dolores Min˜ ana, Carmina Montoliu, Marta Llansola,Santiago Grisolı ´a, Vicente Felipo * Laboratory of Neurobiology, Instituto de In6estigaciones Citologicas, Fundacio´n Valenciana de In6estigaciones Biome´dicas, Amadeo de Saboya, 4 , 46010 Valencia, Spain Accepted 27 March 1998 Abstract The aim of this work was to assess whether nicotine prevents glutamate neurotoxicity in primary cultures of cerebellar neur to try to identify the receptor mediating the protective effect and to shed light on the step of the neurotoxic process which is prevented by nicotine. It is shown that nicotine prevents glutamate and NMDA neurotoxicity in primary cultures of cerebellar neurons. The protective effect of nicotine is not prevented by atropine, mecamylamine or dihydro-b-erythroidine, but is slightly prevented by hexamethonium and completely prevented by tubocurarine and a-bungarotoxin, indicating that the protective e is mediated by activation of a7 neuronalnicotinic receptors. Moreover,a-bungarotoxin potentiates glutamate neurotoxicity, suggesting a tonic prevention of glutamate neurotoxicity by basal activation ofnicotinic receptors. Nicotine did notprevent glutamate-induced rise of free intracellular calcium nor depletion of ATP. Nicotine prevents glutamate-induced proteolysis of t microtubule-associated protein MAP-2 and disaggregation of the neuronalmicrotubularnetwork.The possible mechanism responsible for this prevention is discussed. © 1998 Elsevier Science Ltd. All rights reserved. Keywords : Nicotine;Glutamate neurotoxicity; a7 Nicotine receptors; MAP-2; NMDA receptor; Neurodegeneration 1.Introduction Glutamate is the main excitatory neurotransmitter in mammals. However,excessive activation of glutamate receptorsleadsto neuronaldegeneration and death. Glutamate neurotoxicity is involved in the origin of some neurodegenerative diseases,including amy- otrophic lateral sclerosisand Huntington’sdisease. Glutamate neurotoxicity is also involved in the neu- ronal damage found in cerebral ischemia and ithas been proposed that it is also involved in the origin of Alzheimer’s and Parkinson’s diseases. The understand- ing of the molecular mechanism of glutamate neurotox- icity and of possible mechanisms to prevent it would be therefore ofgreatinterestfor the treatment of these diseases. In many systems, including primary cultures of cere- bellar neurons, glutamate neurotoxicity is mainly medi- ated by excessiveactivation ofthe NMDA type of glutamate receptor (Choi, 1987;Novelli et al., 1988; Min˜ ana et al., 1996). It has been reported that nicotine protectscultured striatal neuronsagainstNMDA re- ceptor-mediated neurotoxicity(Marin et al., 1994). Nicotine has also a neuroprotective effect in an animal modelof excitotoxicity (Borlongan et al., 1995;Shytle et al.,1997). The aim of this work was to assess whether nicotine prevents glutamate neurotoxicity in primary cultures of cerebellar neurons, to test whether the protective effect of nicotine is mediated by some specific receptor, and to shed lighton the step ofthe glutamate-induced neu- ronal death process that is interfered with by nicotine. It is shown thatnicotine prevents glutamate-induced neuronaldeath in primary cultures of cerebellar neu- rons.The protective effect is completely prevented by * Correspondingauthor. Tel.: +34 6 3391250;fax: +34 6 3601453; e-mail: vfelipo@ochoa.fib.es. 0028-3908/98/$19.00 © 1998 Elsevier Science Ltd. All rights reserved. PII: S0028-3908(98)00074-4